Voltage is the pressure of the electricity. Almost like turning on your garden hose, a certain amount of water coming through it is based on the pressure. If you turn up the pressure at the water meter, then more water comes through because of the higher pressure. Likewise, turn up the voltage, then more electricity comes through the wire because of the higher pressure.
Amps is the amount of electricity passing through the wire. For instance, a 3/4" dia. garden hose allows more water to pass through it than a 5/8" dia. garden hose. A 1" dia. pvc pipe allows even more water yet to pass through it than the 3/4" dia. hose. Likewise again, a bigger diameter electrical wire will allow more electricity to pass through it than a smaller wire will.
Watts is simply a power rating, calculated by multiplying the volts and the amps. For instance, 10 amps x 12 volts = 120 watts. And at the same time, 1 amp x 120 volts also equals 120 watts. 1/10 of an amp (.1 amps) x 1200 volts once again equals 120 watts. You can have a very small diameter of wire that will handle a very large voltage, but it can't handle very much amperage at all. You need to have a bigger wire to allow more amperage, and then you won't need as much voltage to push it through the wire.
Your 10 amp G-scale power supply shouldn't even come close to blowing a 15 amp fuse (or tripping a breaker), provided nothing else on that circuit is currently drawing more than a total of 5 amps of electricity. Chances are even quite good that your 10 amp power supply will not even be using a full 10 amps during operation, anyway. If it is, you need a bigger power supply, and possibly a bigger circuit!